Actuator for momentary closure of an elastic diaphragm switch

ABSTRACT

An elastic diaphragm switch is operated by moving a ribbon along a predetermined path obstructed by a bearing surface on a hammer. A projection on the ribbon presses against the bearing surface on the hammer, displacing the hammer against a spring supporting the hammer. Once the hammer is fully displaced, the ribbon passes beyond the bearing surface releasing the hammer to strike the elastic diaphragm of a switch, thereby momentarily closing the elastic diaphragm switch.

United States Patent Harris et al.

[54] ACTUATOR FOR MOMENTARY CLOSURE OF AN ELASTIC DIAPHRAGM SWITCH [72]Inventors: Richard H. Harris; George J. Laurer, both of Raleigh, NC.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

[22] Filed: Mar. 31, 1970 [21] Appl. No.: 24,309

[52] US Cl ..200/160, 200/159 B [51] Int. Cl. ..H0lh 13/50 [58] Field ofSearch ....200/l60,159 B, 86,153 W, 200/46 [56] References Cited UNITEDSTATES PATENTS 3,375,340 3/1968 Wright ..200/l60 3,494,550 2/1970 Hayeset a1. ZOO/I59 B UX 3,392,252 7/l968 Crawford et al. ..200/l60 3,l53,l3010/1964 3,350,5l8 10/1967 Nenninger Krakinowski et al.

[451 May9, 1972 FOREIGN PATENTS OR APPLICATIONS 546,001 3/1956 BelgiumZOO/16 0 962,745 7/1964 Great Britain ..200/l53W OTHER PUBLICATIONS R.H. Harris & L. H. Sedaris, Switch"; I.B.M. Technical Disclosure Vol. 12,No.7, p. 1130; Dec., 1969.

Primary Examiner-Robert K. Schaefer Assistant ExaminerRobert A.Vanderhye Attorney-Hanifin and Jancin and J. .lancin, Jr.

[5 7] ABSTRACT An elastic diaphragm switch is operated by moving aribbon along a predetermined path obstructed by a bearing surface on ahammer. A projection on the ribbon presses against the bearing surfaceon the hammer, displacing the hammer against a spring supporting thehammer. Once the hammer is fully displaced, the ribbon passes beyond thebearing surface releasing the hammer to strike the elastic diaphragm ofa switch, thereby momentarily closing the elastic diaphragm switch.

7 Claims, 6 Drawing Figures PATENTEUMY 9 mi? FIG. 2

FIG.

FIG.3

FIG. 6

FIG.5

BACKGROUND OF THE INVENTION 1. Field of the Invention The inventionrelates to the field of momentary closure switches, and moreparticularly to the field of such switches which are adaptable tokeyboard use.

2. Description of the Prior Art Prior art ribbon actuated keyboards haveused mechanical decoding to determine which key was depressed. Thecommon mechanical decoding systems require that one key be releasedbefore a subsequent key is depressed. If one key is depressed prior tothe release of the preceding key, the decoding system will decodeinaccurately. Therefore, interlocking systems are required to preventdepression of more than one key at a time. This requirement causes askilled operator to work slower than he is capable of working.

Prior art momentary contact switches must be replaced as a unit uponfailure of the actuator or the contacts because it has been commonpractice to build their structure and mechanism as a unit. Thus, thereplacement of an actuator requires replacing the unit which is costly.Replacement of just the actuator, for example, would take considerablylonger, if it were possible, and would be even costlier.

It is known in the prior art to have an elastic diaphragm switch heldclosed by a spring loaded actuator. Such switches are not useful forthose keyboard applications which require momentary contact.

The prior art has no momentary actuator which controls the forcesufficiently to preserve the elastic diaphragm switch.

For the purpose of this invention, a ribbon is an elongate member, whichmay be either rigid or flexible.

OBJECTS The primary object of the invention is to actuate a momentarycontact switch in an improved manner.

Another object is to actuate a momentary contact switch by an impulseimpact force striking all of the switch members.

A further object is to construct an actuator and switch contacts of amomentary contact switch separately instead of as a unit so that theycan be individually replaced.

Still another object is to control the striking force of an actuator ona weak momentary contact switch member so the force is not so great asto damage the switch member and yet is strong enough to obtain quickmomentary contact response time.

SUMMARY OF THE INVENTION The above objects are accomplished by providinga momentary closure switch having a housing in which an actuator isslidably mounted. One or more small hammers, each having a bearingsurface, are attached to the housing by cantilever springs. The actuatorcomprises a ribbon which has a projection integral with it. Theprojection presses against the bearing surface of the hammer duringactuation. The projection on the ribbon displaces the hammer, storingenergy in a spring. After the hammer reaches maximum displacement it isreleased by the projection passing beyond the bearing surface. Uponbeing released the hammer overthrows its rest position, striking amembrane switch to momentarily close the switch. The force generated bythe hammer is determined by the mass of the hammer, the length ofdisplacement of the hammer, the length of the spring, the springconstant and the spacing of the switch member to be struck. During thereturn of the actuator the projection on the ribbon passes over thehammer without actuating the switch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of theactuator showing the switch in its rest position.

FIG. 2 is a perspective view of the actuator in partial section showingthe switch immediately after momentary actuation.

FIG. 3 is a view showing the ribbon's projection in relation to thehammers bearing surface while they are in rest position.

FIG. 4 is a view showing the ribbon's projection and the hammer in thehammers position of maximum displacement, just prior to release.

FIG. 5 is a view showing the hammer striking the membrane switch duringoverthrow, after release of the hammer.

FIG. 6 is a view showing the projection of the ribbon passing over partof the hammer in returning to the switchs rest position.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIGS. 1 and 2 andparticularly FIG. 2, a switch is generally shown at and is comprised ofactuator means 1 10, housing means 130, impulse impact means 150, andswitch means 180.

Actuator means is comprised of a depressable keystem 112 and ribbons 114and 118. Keystem 112 is slidably mounted in housing means 130. Each ofthe ribbons has two projections near one end, 115 and 1 16.

Housing means is comprised of a keystem guide 132 of guiding keystem112, inclined ramps 134 and 136 for guiding the ribbons 114 and 118;keystem return spring 138 for biasing keystem 112 to its rest position,and return spring supports 140, 142 and 144 for supporting the returnspring.

The impulse-impact means is comprised of hammers 154, hammer supportsprings 164, which attach the hammers 154 to the housing 132 and supportthe hammers in their rest positions.

As shown in FIG. 3, hammer 154 has a bearing surface 172, against whichprojection 116 of ribbon 114 presses to move the hammer. I-Iammer 154also has a projection 174 on its lower face which strikes switch meansduring actuation.

Switch means 180 is comprised of four elastic diaphragm switches 184,which are momentarily closed when struck by hammers 154. There is anadditional elastic diaphragm switch (EDS) located under the lower end ofkeystem 112. EDS 190 is actuated when keystem 112 is fully depressed.Although an elastic diaphragm switch is used in the preferredembodiment, any small displacement switch operable by a small mechanicalforce can be used. Alternatively one of the contacts can be on thehammer and the other can be struck by the hammer. Any force transducersensitive to the force applied by the hammer can be used as the switchmeans.

In the preferred embodiment the ribbons 114 and 118 are flexible andfollow a curved path. The curved path is determined by inclined ramps134 and 136 which guide the flexible ribbons. However, the ribbons maybe straight and either rigid and self-supporting or flexible andsupported by straight ramps. If straight ribbons are used they wouldmove parallel to the length of the keystem 112 and deflect the hammers154 in a direction substantially perpendicular to the keystem.Therefore, the elastic diaphragm switches would be mounted parallel tothe keystem rather than perpendicular to it as in the preferredembodiment. The number of ribbons and hammers may be easily variedaccording to the number of elastic diaphragm switches to be actuated bythe actuator.

The ribbons 114 and 118 can be pulled, rather than pushed, by thedepression of the keystem 112. This is accomplished by repositioning theinclined ramps 134 and 136 and by attaching ribbons 114 and 118 tokeystem 112 at its lower end, so that the ends of the ribbons with theprojections are nearer the upper end of the keystem. In thisconfiguration depression of the keystem pulls the ribbon downward. Forthis embodiment the hammers and the elastic diaphragm switches must berelocated so that the hammers are activated by the ribbons and strikethe switches.

Alternatively, a slide switch, rather than a push button switch, can beused. In such an arrangement the ribbons would be activated by the slideswitch movement in a fashion similar to that of the push buttonembodiment. The hammers and the elastic diaphragm switches would then beplaced where the ribbons actuate the hammer.

The invention is not restricted to these embodiments, but is usable inany embodiment which provides for an impulse-impact to the elasticdiaphragm switches.

The switch 100 is preferably formed of molded plastic parts. The switch100 may be molded in sections and the sections then glued or weldedtogether to form the final assembly 100.

The ribbons 114 and 118 and the keystem 112 are preferably made from thesame plastic material and acetal resin is preferred because it has goodwear characteristics, It is preferred to mold the ribbons as an integralpart of the keystem. However, if desired, the ribbons may be formedseparately and glued or attached to the keystem in any other acceptablemanner.

OPERATION OF THE INVENTION The operation of the preferred embodimentwill be described with respect to FIGS. 2-6, and especially FIGS. 3-6.For clarity the operation of switch 100 will be described in terms ofribbon 1 14, projection 1 16 and just one hammer 154, although thedescription applies equally to both ribbons and to every hammer.

in FIGS. 4, 5 and 6 the lower end of ramp 134 and all ofthe ribbon 114,except for projection 116, have been left out of the drawing to simplifythe drawings and emphasize the significant relationships. These drawingsshow the relationship between hammer projection 174 and bearing surface172 and between hammer projection 174 and elastic diaphragm switch 184at different points during an actuation cycle.

To actuate switch 100, keystem 112 is depressed. As keystem 112 isdepressed, ribbon 114 moves down inclined ramp 134 and projection 116 onthe ribbon engages bearing surface 172 of hammer 154. As keystem 112 isfurther depressed, hammer 154 is displaced from its rest position byprojection 116 on ribbon 114 which is moving along and is supported byramp 134. As keystem 1 12 is further depressed, but before it is fullydepressed, projection 116 passes beyond bearing surface 172, releasinghammer 154 which is driven back toward its rest position by spring 164.Spring 164 develops sufficient momentum in hammer 154 to cause thehammer to overthrow its rest position and strike elastic diaphragmswitch 184. The noise made by the contact of hammer 154 with EDS 184provides audible feedback to the person depressing keystem 112indicating that switch 100 has been activated. In addition, ribbon 114moves more easily after projection 116 passes beyond bearing surface 172because there is less resistance to the movement of the ribbon. Thiseasier movement provides a mechanical or tactile feedback to the personpressing the keystem. Hammer 154 striking EDS 184 momentarily closeselastic diaphragm switch 184. The period for which switch 184 is closeddepends on the mass of the hammer, the spring constant, and the lengthof spring 164, and on the characteristics of the elastic diaphragmswitch 184. When keystem 112 is fully depressed, the lower end of thekeystem presses on elastic diaphragm switch 190, closing switch 190 foras long as keystem 112 is fully depressed in order to indicate that thekeystem is fully depressed.

On the return stroke of keystem 112, projection 116 on ribbon 114 passesover hammer 154, depressing the hammer slightly but not enough to causethe hammer to strike EDS 184. Therefore, switch 184 is activated only onthe depression stroke of keystem 112. When keystem 112 has returned toits initial position, projection 116 has passed over hammer 154 and isagain in a position to press on the bearing surface 172 when the keystemis depressed.

For situations in which it is considered desirable, the harnmers bearingsurface may be reversed and the hammer may be actuated on the returnstroke of keystem 112, rather than on the depression stroke as in thepreferred embodiment. In a situation where it is desired to know thatthe switch has returned to an actuatable condition, some hammers may beactuated on the depression stroke and others actuated on the returnstroke. This is best accomplished by providing two ribbons as in thepreferred embodiment and having one ribbon activate its hammers on thedepression stroke and the other ribbon activate its hammers on thereturn stroke. Some situations in which it would be desirable to knowthat the push button has returned to an actuatable condition are wherethe button sounds a warning alarm or is used to activate a securitydevice of some variety.

What is claimed is:

1. A momentary closure switch comprising:

housing means,

a depressable keystem slideably mounted in the housing means, saidkeystem having a rest position, said keystem being in its rest positionat the beginning and at the end of each actuation and moving from itsrest position to a second position and back to its rest position duringeach actuation;

at least one ribbon attached to the keystem, said ribbon beingpositioned for longitudinal movement and having at least one projectionintegral with it, said projection extending transverse to the ribbonsdirection of movement and following a predetermined path when thekeystem is depressed,

at least one hammer attached to the housing by a cantilever spring, thehammer having a bearing surface disposed in the predetermined path, inorder that the ribbon may displace the hammer during a first part of anactuation stroke of the keystem, and may release the hammer during asecond part of the actuation stroke; and

a normally open elastic diaphragm switch strikeable by the hammer, saidswitch closing momentarily for a predetermined time, when struck by thehammer.

2. The switch of claim 1 wherein:

the ribbon is flexible, and;

the predetermined path is curved.

3. A momentary closure switch comprising:

housing means;

actuator means movably mounted in the housing means, said actuator meanshaving a rest position and being in its rest position at the beginningand at the end of each actuation, and moving from its rest position to asecond position and back to its rest position during each actuatron;

impulse impact means attached to the housing means, and operable by theactuator means, said impulse impact means comprising at least one hammerattached to the housing means by a cantilever spring;

normally open switch means engageable by the impulse impact means, saidswitch means closing momentarily for a predetermined time, when engagedby the impact means, and being closed only once for each actuation ofthe actuator means.

4. The switch in claim 3 wherein the switch means is an elasticdiaphragm switch.

5. The switch of claim 3 wherein the actuator means comprises:

a keystem having a ribbon attached to it, the ribbon having a projectionintegral with it, said ribbon being flexible and guided along apredetermined path by the housing means.

6. A momentary closure switch comprising:

housing means;

actuator means movably mounted in the housing means, said actuator meanshaving a rest position and being in its rest position at the beginningand at the end of each actuation, and moving from its rest position to asecond position and back to its rest position during each actuation,said actuator means having a ribbon attached to it, the ribbon having aprojection integral with it; and

impulse impact means attached to the housing means, operable by theactuator means, said impulse means further comprising a spring supportedhammer having a bearing surface which is disposed in the path followedby the projection of the ribbon, in order that the ribbon may displacethe hammer;

normally open switch means engageable by the impulse impact means, saidswitch means closing momentarily for a predetermined time, when engagedby the impact means, and being closed only once for each actuation ofthe actuator means. 5

7. The switch of claim 6 wherein the switch means is an elasticdiaphragm switch.

1. A momentary closure switch comprising: housing means, a depressablekeystem slideably mounted in the housing means, said keystem having arest position, said keystem being in its rest position at the beginningand at the end of each actuation and moving from its rest position to asecond position and back to its rest position during each actuation; atleast one ribbon attached to the keystem, said ribbon being positionedfor longitudinal movement and having at least one projection integralwith it, said projection extending transverse to the ribbon''s directionof movement and following a predetermined path when the keystem isdepressed, at least one hammer attached to the housing by a cantileverspring, the hammer having a bearing surface disposed in thepredetermined path, in order that the ribbon may displace the hammerduring a first part of an actuation stroke of the keystem, and mayrelease the hammer during a second part of the actuation stroke; and anormally open elastic diaphragm switch strikeable by the hammer, saidswitch closing momentarily for a predetermined time, when struck by thehammer.
 2. The switch of claim 1 wherein: the ribbon is flexible, and;the predetermined path is curved.
 3. A momentary closure switchcomprising: housing means; actuator means movably mounted in the housingmeans, said actuator means having a rest position and being in its restposition at the beginning and at the end of each actuation, and movingfrom its rest position to a second position and back to its restposition during each actuation; impulse impact means attached to thehousing means, and operable by the actuator means, said impulse impactmeans comprising at least one hammer attached to the housing means by acantilever spring; normally open switch means engageable by the impulseimpact means, said switch means closing momentarily for a predeterminedtime, when engaged by the impact means, and being closed only once foreach actuation of the actuator means.
 4. The switch in claim 3 whereinthe switch means is an elastic diaphragm switch.
 5. The switch of claim3 wherein the actuator means comprises: a keystem having a ribbonattached to it, the ribbon having a projection integral with it, saidribbon being flexible and guided along a predetermined path by thehousing means.
 6. A momentary closure switch comprising: housing means;actuator means movably mounted in thE housing means, said actuator meanshaving a rest position and being in its rest position at the beginningand at the end of each actuation, and moving from its rest position to asecond position and back to its rest position during each actuation,said actuator means having a ribbon attached to it, the ribbon having aprojection integral with it; and impulse impact means attached to thehousing means, operable by the actuator means, said impulse meansfurther comprising a spring supported hammer having a bearing surfacewhich is disposed in the path followed by the projection of the ribbon,in order that the ribbon may displace the hammer; normally open switchmeans engageable by the impulse impact means, said switch means closingmomentarily for a predetermined time, when engaged by the impact means,and being closed only once for each actuation of the actuator means. 7.The switch of claim 6 wherein the switch means is an elastic diaphragmswitch.